[Suppressibility of thyroid autonomy in endogenous and additional exogenous TSH suppression in patients with thyroid autonomy].
OBJECTIVE
The aim of this retrospective study was to examine the effect of an additional exogenous thyroid hormone suppression on the 99m Technetium Thyroid-Uptake (TcTU) in patients with thyroid autonomy and endogenous TSH suppression.


METHODS
21 patients were examined in the years 1992-1996; they had a primary endogenous suppression (end) of the TSH-b and an evaluation of the TcTU. After an additional exogenous suppression (ex) of the thyroid, the first two weeks with 75 micrograms/dl and the following 2 weeks 150 micrograms/d, or depending on the bodyweight 2 micrograms/kg levothyroxin, another evaluation of the TcTU was performed. The whole patients were called group I with a TcTUend of 1.6%-7.4%. The subgroups were selected by thresholds of the TcTUend; group Ia TcTUend > or = 1.6% and < 2.5%, group lb TcTUend > or = 2.5%, group Ic TcTUend > or = 3%.


RESULTS
The intraindividual comparison showed a significant decrease of the autonomous "volume" after exogenous suppression with levothyroxin. This is shown by the following values of the TcTU: group I TcTUend = 3.47 +/- 1.65 and TcTUex = 2.91 +/- 1.38, which means a reduction of 20 rel.% (p < or = 0.001); group Ia TcTUend = 2.05 +/- 0.27, TcTUex = 1.85% +/- 0.22, which means 10 rel.% (p < or = 0.001); group Ib TcTUend = 4.18 +/- 1.59, TcTUex = 3.45% +/- 1.34, which means 20 rel.% (p < or = 0.001); group Ic TcTUend = 5.00% +/- 1.43, TcTUex = 4.05% +/- 1.32, which means 20 rel.% (p < or = 0.001).


CONCLUSIONS
Supposing a structural variability of autonomous thyroid tissue with heterogenous TSH receptors our study shows a significant additional exogenous suppression in already endogenous suppressed TSH receptors.
Herrmann
A
A
Abteilung für Nuklearmedizin, Universität Göttingen, Deutschland.
Gratz
S
S
Behr
T
T
Meller
J
J
Becker
W
W
D000328:Adult; D000368:Aged; D006801:Humans; D006980:Hyperthyroidism / Q000000981:diagnostic imaging*; D008875:Middle Aged; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013667:Technetium; D013961:Thyroid Gland / Q000033:anatomy & histology* / Q000000981:diagnostic imaging* / Q000502:physiology; D013972:Thyrotropin; D013974:Thyroxine
D019275:Radiopharmaceuticals; D013667:Technetium; D013972:Thyrotropin; D013974:Thyroxine
Supprimierbarkeit autonomen Schilddrüsengewebes unter endogener und zusätzlicher exogener TSH-Suppression bei Patienten mit Schilddrüsenautonomie.